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Koleksiyondaki öğeler
- MakaleAçık Erişim2015Scopus SJRQ2Utilization of the limit equilibrium and finite element methods for the stability analysis of the slope debris: An example of the Kalebasi District (NE Turkey)
Alemdag, Selcuk; Kaya, Ayberk; Karadag, Mustafa; Gurocak, Zulfu; Bulut, Fikri
The stability of the slope debris in residential area of the Kalebasi District (Ozkurtun-Gumushane) was investigated using the Limit Equilibrium (LE) and Finite Element Shear-Strength Reduction (FE-SSR) methods. Along the survey lines, four trial pits were dug and fourteen boreholes having a total length of 345m were drilled. Also, seismic refraction studies were conducted along the five lines. According to the field studies, thickness of the slope debris covering the 98ha of the study area varies between 1 and 36m. To determine the physical and shear strength properties of the slope debris, undisturbed samples were taken from the trial pits. As a result of the laboratory tests, soil categories of the debris were found to be as Clayey Sand (SC), Silty Sand (SM) and Low Plasticity Clay (CL). The deformation-controlled shear box tests were carried out to determine the shear strength parameters of the slope debris. According to these tests it was found that the peak cohesion and peak friction angle varies between 2.63-16.35kN/m2 and 20-27°, respectively. Stability analyses were performed using the obtained data from field and laboratory investigations in the Slide v5.0 and Phase2 v6.0 software programs and results were compared. In LE stability analyses, the factor of safety (FOS) of survey lines were found to be as 1.44, 1.80, 1.96, and 1.72; however for the FE-SSR method they were determined as 1.39, 1.72, 1.59, and 1.58, respectively.
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İncele - MakaleYalnız künye2012Scopus SJRQ3Analysis of the multi-item dimensionality of patients' perceived value in hospital services
Teke, Abdulkadir; Cengiz, Ekrem; Çetin, Mehmet; Demir, Cesim; Kirkbir, Fazil; Fedai, Turan
The purpose of this research is to analyse the multi-item dimensionality of patients' perceived value in hospital service. A total of 564 patients administered to Gulhane Military Medical Academy were surveyed. Sample population was specified through convenience sampling procedure. A face to face survey was conducted by three interviewers in August 2008. Confirmatory Data Analysis was carried out to reach the final data analysis. A scale of overall perceived value in health service was developed, which was composed of three dimensions and represented by 21 items. These dimensions were: Functional value, emotional value, and social value. The results indicated that perceived value was a multidimensional construct that affects the whole process of service purchasing. If the hospitals managers give importance to the sub-dimensions of the patient value inclined to their own hospitals and they regularly examine the situation of these dimensions, they can move one step ahead in achieving patient satisfaction and loyalty.
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İncele - MakaleYalnız künye2011Scopus SJRQ3Applicability of excavatability classification systems in underground excavations: A case study
Kaya, Ayberk; Bulut, Fikri; Alemdaǧ, Selçuk
In this study, applicability of the excavatability classification systems in underground excavations is investigated. For this purpose, the entrance portal of the Konakönü (Arakli{dotless}-Trabzon) tunnel, excavated in volcanic rocks within the scope of Black Sea coastal highway project, is chosen as pilot study area. The entrance portal of tunnel is excavated through the rocks of Eocene-aged Kabaköy formation of basaltic-andesitic tuffs, aglomerate and basalt. In excavation, basaltic and andesitic tuffs were ripped by using hydraulic breaker; aglomerate and basalt were excavated by using explosives. Based on the results obtained from field and laboratory studies, rock masses are classified in terms of excavatability. According to Pettifer and Fookes (1994), basaltic and andesitic tuffs are included in "hard ripping", aglomerate and basalt in "blasting required" categories. With reference to Tsiambaos and Saroglou (2009), basaltic and andesitic tuffs fall in "ripping", agglomerate and basalt in "hammer and blasting" categories. It was found out that the classifications made according to these two methods are completely compatible with in-situ excavation works. Also, it is determined that the parameters give the best results for determining excavation class in underground excavations are GSI (Geological Strength Index), I s (50) (Point load strength index) and I f (Discontinuity spacing index).
AtıfScopus14İncele - MakaleYalnız künye2011Scopus SJRQ3An approximate solution of a model for HIV infection of CD4+ T cells
Merdan, M.; Gokdogan, A.; Erturk, V.S.
In this paper, the approximate solution of the differential system modeling HIV infection of CD4+ T cells is obtained by a reliable algorithm based on an adaptation of the standard variational iteration method (VIM), which is called the multi-stage variational iteration method(MSVIM). A comparison between MSVIM and the fourthorder Runge-Kutta method (RK4-method) reveal that the proposed technique is a promising tool to solve the considered problem.
AtıfScopus14WoS13İncele - MakaleAçık Erişim2015Scopus SJRQ1N-Acylsulfonamides strongly inhibit human carbonic anhydrase isoenzymes i and II
Yildirim, Alper; Atmaca, Ufuk; Keskin, Ali; Topal, Meryem; Çelik, Murat; Gülçin, Ilhami; Supuran, Claudiu T.
Sulfonamides represent a significant class of biologically active compounds that inhibit carbonic anhydrase (CA, EC.: 4.2.1.1) isoenzymes involved in different pathological and physiological events. Sulfonamide CA inhibitors are used therapeutically as diuretic, antiglaucoma, antiobesity and anticancer agents. A series of new sulfonamides were synthesized using imides and tosyl chloride as starting materials. These N-acylsulfonamides efficiently inhibited the cytosolic human carbonic anhydrase isoenzymes I, and II (hCA I, and II), with nanomolar range inhibition constants ranging between 36.4 ± 6.0-254.6 ± 18.0 and 58.3 ± 0.6-273.3 ± 2.5 nM, respectively.
AtıfScopus158WoS155İncele - MakaleYalnız künye2011Scopus SJRQ1Experimental and analytical system identification of Eynel arch type steel highway bridge
Altunişik, Ahmet Can; Bayraktar, Alemdar; Sevim, Bariş; Özdemir, Hasan
This paper describes a full scale arch type steel highway bridges, its finite element modelling and Operational Modal Analysis. Eynel Highway Bridge which has arch type structural system with a total length of 336 m and located in the AyvacIk county of Samsun, Turkey is selected as a case study. The bridge connects the villages which are separated with Suat Uǧurlu Dam Lake. The three dimensional finite element model is constructed using project drawings and an analytical modal analysis is then performed to generate natural frequencies and mode shapes in the three-orthogonal directions. The ambient vibration tests on the bridge deck under natural excitation such as traffic, human walking and wind loads are conducted using Operational Modal Analysis. Sensitive seismic accelerometers are used to collect signals obtained from the experimental tests. To obtain experimental dynamic characteristics, two output-only system identification methods are employed namely, Enhanced Frequency Domain Decomposition method in the frequency domain and Stochastic Subspace Identification method in time domain. The correlation between the finite element model and experimental results is studied. Good agreement is found between dynamic characteristics in the all measurement test setups performed on the bridge deck. It is demonstrated that the ambient vibration measurements using Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification methods are enough to identify the most significant modes of steel highway bridges. It is seen that there are some differences between analytical and experimental natural frequencies and experimental natural frequencies are generally bigger than the others.
AtıfScopus44WoS41OpenAlex39İncele - MakaleYalnız künye2013Scopus SJRQ1Effects of charge properties on exergy balance in spark ignition engines
Sezer, Ismet; Bilgin, Atilla
This study investigates the effects of the air-fuel mixture (charge) properties on the exergy balance in spark ignition engines. A thermodynamic cycle model including compression, combustion and expansion processes is used. The principles of the second law are applied to the cycle model to perform an exergy analysis. Variation of the exergetic variables during the investigated portion of the cycle are examined as a function of the charge properties, i.e., fuel-air equivalence ratio, residual gas fraction and initial charge temperature. The results show that increasing fuel-air equivalence ratio causes an increase in irreversibilities and also exergy losses with heat transfer and exhaust gases, but enriching the air-fuel mixture beyond the stoichiometric ratio makes no significant contribution to the exergy transfer with work transfer. A slightly lean mixture also gives the best first and second law efficiencies. It is observed that there is a linear relation between the residual gas fraction and the exergetic variables. An increase in the residual gas fraction decreases the irreversibilities and exergy losses aside from the exergy transfer with work transfer. However, increasing the residual gas fraction positively affects the first and second law efficiencies because of the diluting of the charge. Increase of initial charge temperature creates a reduction in the irreversibilities and the exergy losses and, it also results in a lower exergy output by work transfer. Further, increase of initial charge temperature negatively influences the first and second law efficiencies.
AtıfScopus32WoS28OpenAlex40İncele - MakaleYalnız künye2012Scopus SJRQ2Monte Carlo modelling of human body for dose conversion coefficients of 137Cs in soil of the Eastern Black Sea region of Turkey
Çelik, Necati
Absorbed dose conversion coefficients for a human body standing on the soil surface were calculated for 137Cs in the soil of Eastern Black Sea region of Turkey using the Monte Carlo simulation method. The results were given in nGy h -1 per Bq cm -2 as a function of depth. Simple numerical integration of this function multiplied with the known specific activity as a function of depth gives the absorbed dose conversion coefficients for any distribution of 137Cs in soil. Gaussian distribution of 137Cs in the soil was considered for calculations.
AtıfScopus1WoS1OpenAlex1İncele - BildiriYalnız künye2015Spatial variations of seismotectonic b and Dc-values in and around the East Anatolian Fault Zone (EAFZ), Turkey
Öztürk, S.; Sari, M.
An evaluation of recent seismicity behaviors in the East Anatolian Fault Zone, eastern part of Turkey, is made by using Gutenberg-Richter b-value and fractal dimension Dc-value. Reasenberg's algorithm is used in order to separate the dependent events from independent ones. The completeness magnitude in study region is calculated as 2.8. b-value is calculated as 1.02+/-0.01 by maximum likelihood estimation and matches the Gutenberg-Richter law with a b-value typically close to 1. Dc-value is found as 2.34+/-0.04 with 95% confidence limit by linear regression and this large value suggest that seismicity is more clustered at larger scales in the East Anatolian Fault Zone. The smallest b-values and the highest Dc-values are found in the same areas covering the East Anatolian Fault Zone, Aşkale Fault, Sancak-Uzunpinar Fault Zone, Pülümür Fault, Göynük Fault Zone and Genç Fault, in and around Karataş-Osmaniye Fault Zone and in the southeast part of the study region. Thus, low b-value in these regions may be an indication of low degree of heterogeneity, high-strain due to the active tectonics and stress to build up over time and to be released by events. Thus, special attention should be given to these regions where low b-value and large Dc-value are observed.
- MakaleYalnız künye2010Scopus SJRQ2Curie-point depth from spectral analysis of magnetic data in erciyes stratovolcano (Central Turkey)
Maden, Nafiz
Curie-point depth and heat flow values of the Erciyes region are determined to identify the thermal regime of the Central Anatolia by applying the spectral analysis method to the magnetic anomaly data. To compute the spectrum of the data, the magnetic anomaly of the region is transformed into 2-D Fourier domain to attain the average Curie depth. This method is useful in determining the top boundary of magnetic anomaly sources and reveals the Curie depth as 13.7 km in the study area. The obtained results imply a high thermal gradient (42.3°C km-1) and corresponding heat flow values (88.8 mWm-2) in the research area. Using the temperature value measured at borehole drilled by the General Directorate of Mineral Research and Exploration of Turkey (MTA), the values for the thermal gradient and heat flow value were computed as 50.7°C km-1, 106.5 mWm-2. From the heat flow value, the Curie-point depth was determined as 11.4 km in this region. It is concluded from the obtained values that the region has very high geothermal potential caused by partial melting of the lower crust.
AtıfScopus61WoS55OpenAlex68İncele - MakaleYalnız künye2012Scopus SJRQ2Antifungal activity of Trachystemon orientalis L. aqueous extracts against plant pathogens
Onaran, Abdurrahman; Yilar, Melih
Trachystemon orientalis (L.) G. Don (Boraginaceae), recognized as Hodan, Kaldirik in Turkey, is a perennial medical plant. The plant materials of Kaldirik were collected from Saz village of Düzce province (Turkey) in 2010 to determine its antifungal effect. The aqueous extracts obtained from leaves, roots and flowers and were applied against five plant pathogen fungi which they are respectively Ascochyta rabiei (Pass) Labr., Fusarium oxysporum (Schlechtendahl:Fries) f. sp. melonis (Snyder & Hansen), Fusarium oxysporum (Schlechtendahl:Fries) f. sp. radicis-lycopersici (Jarvis & Shoemaker), Verticillium dahliae (Kleb.) and Rhizoctonia solani Kühn. The original concentration of extracts obtained for fungal studies was 10% as. Sterile potato dextrose agar (PDA) was cooled in a water bath at 40°C, and the extracts were mixed with the sterile 250 ml PDA to obtain final concentrations of 1%, 3%, 5%, 7% 10% and 20%. Then, the PDA was poured into 60-mm Petri plates (10 ml plate-1) and a agar disc (5 mm in diameter) of plant pathogens (from 7 day-old PDA cultures) were inoculated on medium. They were incubated at 25±2°C for 7 days in incubator. As a result of the study, the aqueous extract of flower showed maximum inhibitory effect against the mycelial growth of plant pathogens, it was respectively followed by leaf and root extracts. Flower extract completely inhibited mycelial growth of A. rabiei, V. dahliae and R. solani in all applied doses. According to the result of the study, the first time was identified of T. orientalis aqueous extracts, have high antifungal effect against plant pathogens.
AtıfScopus19WoS18İncele - MakaleYalnız künye2013Scopus SJRQ2Effects of different curvature patches on the strength of double-strap adhesive joints
Akpinar, Salih
In general, the damage in adhesively bonded joints initiates from and propagates through the ends of the overlap area due to high stress concentration in that area. The reduction of these stress concentrations results in an increase in the strength of the joints. For this reason, the rounding of the overlap region before bonding and then applying compression during the bonding process will exert compressive residual stresses on the adhesive layer in the overlap end regions. It is known that the residual stresses formed in this process increase the failure strength of the joint and hence delay the initiation of the damage. In this study, the effects of overlap length (L = 50,75, and 100 mm), patch thickness (h = 1.6, 3.2, and 5 mm) and patch materials (AA2024 aluminum alloy, AISI 304 steel, AISI 1040 steel) on bond strength were experimentally investigated for adhesively bonded double-strap joint (DSJ) and curvature double-strap joint (CDSJ) subjected totensile loading. The experimental study showed that the overlap length, patch thickness and patch materials have considerable influence on the failure strength and displacement capacity of the joints.
AtıfScopus31WoS29İncele - Kitap BölümüYalnız künye2014Electronic word-of-mouth: Factors affecting consumer review writing behavior on electronic platforms
Yildiz, Emel; Ayyildiz, Hasan
This chapter examines the effects of word-of-mouth motivations and culture on electronic word-of-mouth behavior. This chapter also focuses on the effects of cultural values on electronic word-of-mouth behavior. Within the context of the study, online forums in which consumers write comments have been used. The data was obtained from an electronic survey provided to 561 consumers. The reliability of scales has been tested via the Cronbach's Alfa Method and the validity of scales has been tested by Factor Analysis. After determining the reliability and validity of the scales, research hypotheses were tested by Structural Equation Modeling (SEM) and Multiple Regression Analysis. The findings show that motivation and culture have positive effects on electronic word-of-mouth behavior. This chapter also attempts to explain the effects of cultural values on electronic word-of-mouth behavior, and it is found that while uncertainty avodiance and masculinity have positive effects, individualism and power distance have negative effects on electronic word-of-mouth behavior.
AtıfOpenAlex1İncele - MakaleAçık Erişim2014Scopus SJRQ3New record of the genus homolophus (Opiliones: Phalangiidae) in Turkey and sem studies on its morphology
Kurt, Kemal
In this study, Homolophus nakhichevanicus Snegovaya, 2012 (Opiliones: Phalangiidae) was recorded in Turkey for the first time. This is only the second known location for this species, the first being the type locality (Nakhichevan Autonomous Republic, Azerbaijan). The morphological characteristics are described along with a scannig electron microscope (SEM) study on the dorsal aspect, crown-shape on cephalothorax, ocularium, chelicera, pedipalp, the first pair of legs. The male genitalia of the specimens are also presented.
AtıfScopus3WoS2OpenAlex2İncele - MakaleYalnız künye2012Scopus SJRQ2Trace and rare earth elements as indicators of provenance and depositional environments of Lias cherts in Gumushane, NE Turkey
Eker, Cigdem Saydam; Sipahi, Ferkan; Kaygusuz, Abdullah
Trace elements and rare earth elements (REEs) of Lias-aged cherts in the Gumushane area were studied in order to understand their origin and depositional environment. Twenty three chert samples from five stratigraphic sections were analysed by inductively coupled plasma-mass spectrometry, X-ray diffraction, and mineralogical investigation. Lias cherts in the study area are microcrystalline, cryptocrystalline quartz, and megaquartz depending on mineralogical content. Trace elements of the cherts were compared with PAAS, Co, Y, and Th had stronger depletions in the five sections, whereas V, Ni, Zr, Nb, and Hf had smaller depletions. The distribution of Zr, Hf, and Ta yields Zr/Hf, Zr/Ta and Hf/Ta ratios (25/645, 37/665, and 0.18/3, respectively) that differ from those of chondrites and average upper continental crust, suggesting that these elements are likely non-detrital but are sourced from seawater. Th/U ratios range from 0.04 to 0.45 and are lower than those of the upper continental crust (average: 3.9). Lias-aged cherts have low total REE abundances and stronger depletions in five sections of the PAAS and chondrite-normalised plots. The cherts are characterised by a positive Eu anomaly (average: 4.9) and LREE-enrichment (LaN/YbN=average: 3.5). In addition, about one-half of the cherts exhibit positive Ce anomaly (range: 0.25-2.58), chondritic Y/Ho values (range: 3.3-60), and low (La/Ce)N values (average: 1.8). REE and trace element abundance in Lias cherts indicate that these elements were likely derived from hydrothermal solutions, terrigenous sources, and seawater. The REE patterns of the cherts show that they were probably deposited close to a continental margin.
AtıfScopus60WoS58OpenAlex62İncele - MakaleYalnız künye2012Scopus SJRQ3Coupling of homotopy perturbation, Laplace transform and Padé approximants for nonlinear oscillatory systems
Merdan, Mehmet; Yildirim, Ahmet; Gökdogan, Ahmet; Mohyud-Din, Syed Tauseef
In this article, homotopy perturbation method coupled with Laplace transform and Padé 0approximants is applied on the re-formulated nonlinear oscillatory systems. Numerical results and graphical represenations explicitly reveal the complete reliability and effeicincy of the suggested algorithm.
AtıfScopus1İncele - MakaleYalnız künye2013Scopus SJRQ1Prediction of offshore bar-shape parameters resulted by cross-shore sediment transport using neural network
Kömü rcü, Murat Ihsan; Kömür, Mehmet Aydin; Akpinar, Adem; Özölçer, Ismail Hakki; Yüksek, Ömer
In order to understand the features of coastal zone and to utilize the coastal areas, it is necessary to determine the sediment movement and the resulting transport. Waves, topographic features, and material properties are known as the most important factors affecting the sediment movement and coastal profiles. In this study, by taking into consideration of wave height and period (H0, T), bed slope (m) and sediment diameter (d50), cross-shore sediment movement was studied in a physical model and various bar-shape parameters of the resultant erosion type profile were determined. Using 80 experimental data which are obtained from physical model studies, a neural network (NN) has been calibrated to predict bar-shape parameters of beach profiles. A sensitivity analysis was firstly carried out to decide data of training and test sets. Four different models, in which the rates of their training and testing set data were 80% and 20%, 70% and 30%, 60% and 40%, 50% and 50% were constituted and their performances were compared. It was determined that the model, in which the rate of its training and testing set data was 80% and 20%, respectively, has the best results. Therefore, a total of 64 experimental data were used as training set and the remainders of the experimental data were used as a testing set for the model. The performance of the NN model was compared with the regression equations developed in a previous study and the equations cited in literature indicating better performance over the equations.
AtıfScopus16WoS14OpenAlex22İncele - MakaleYalnız künye2012Scopus SJRQ1A multistage differential transformation method for approximate solution of Hantavirus infection model
Gökdoĝan, Ahmet; Merdan, Mehmet; Yildirim, Ahmet
The goal of this study is presented a reliable algorithm based on the standard differential transformation method (DTM), which is called the multi-stage differential transformation method (MsDTM) for solving Hantavirus infection model. The results obtanied by using MsDTM are compared to those obtained by using the Runge-Kutta method (R-K-method). The proposed technique is a hopeful tool to solving for a long time intervals in this kind of systems.
AtıfScopus52WoS41OpenAlex54İncele - MakaleAçık Erişim2011Scopus SJRQ1Production of human milk fat substitute with medium-chain fatty acids by lipase-catalyzed acidolysis: Optimization by response surface methodology
Ilyasoglu, Huri; Gultekin-Ozguven, Mine; Ozcelik, Beraat
The aim of this study was to synthesize human milk fat substitute (HMFS) enriched with medium-chain fatty acids (MCFAs) by Lipozyme® RM IM-catalyzed acidolysis. The reaction substrates (tripalmitin, hazelnut oil fatty acids and Neobee® fatty acids) were specially chosen to mimic human milk fats and to enrich HMFS with MCFAs. Substrate molar ratio, reaction temperature and enzyme content were used to model and to optimize the reaction conditions via response surface methodology. The experiment was carried out at the optimal condition generated from the model yielded structured lipids with caprylic acid (12.8 g/100 g), capric acid (10.6 g/100 g) and palmitic acid (30 g/100 g). These values were found similar to the values predicted by the model (15.9 g/100 g, 14.1 g/100 g and 33.3 g/100 g). It can be concluded that the potential use of the structured lipids (SLs) produced in infant formulas provide energy source delivering a reduced calorie value for newborn, term and preterm infants.
AtıfScopus39WoS34OpenAlex41İncele - MakaleYalnız künye2014Scopus SJRQ1Nonmedical Methods to Relieve Low Back Pain Caused by Lumbar Disc Herniation: A Descriptive Study in Northeastern Turkey
Cilingir, Dilek; Hintistan, Sevilay; Yigitbas, Cagla; Nural, Nesrin
Low back pain due to the effects of lumbar disc herniation is a common complaint of patients who often subsequently seek help from medical professionals. It is also a significant health problem which is quite difficult to treat. This descriptive study was conducted to determine nonmedical methods used by patients with lumbar disc herniation to relieve low back pain; the patients' intensity of low back pain when they were admitted to the hospital was also explored. Ninety-two patients with lumbar disc herniation participated in this study, which was carried out at a university hospital in northeastern Turkey. Data were collected using a patient information form and the visual analog scale (VAS). When the patients were admitted to hospital, their mean VAS score was 6.56 ± 2.45. The study results showed that as a first choice nearly all of the patients (94.6%) with lumbar disc herniation preferred consulting with their physicians before to obtain relief for low back pain. However, in addition to seeing their physician, more than one-half of these patients (57.6%) also used nonmedical methods. The primary nonmedical methods were hot/cold compresses, wrapping various substances on the back, and herbal preparations. An increase in pain was noted by 17.0% of patients after using nonmedical methods. Findings indicated that more than two-thirds of patients experienced either no change or an increase in pain after using nonmedical methods to find relief.
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